Interoception as a Foundation of Infant Mental health     

We see interoception as a foundational concept for infant mental health. Our early development of a sense of self is an “embodied” sense of self that occurs prior to the development of a “mindful” sense of self. There has been an ongoing debate since the time of Freud regarding the origin of the self. Is the origin of the self related to the body and the sensory system or is the origin of the self related to social interactions?  Recently, Fotopoulou & Tsdakiris (2017) proposed that “building a mind, and understanding other minds, are embodied and tightly connected processes.” We argue that the constitution of the self is dependent upon the social mentalization of the body and particularly its homeostatic needs. In short, the radical aspect of our proposal is that social interactions do not shape only the reflective (narrative or extended) self and related notions of affect regulation and social cognition. Instead, the most minimal aspects of selfhood, namely the feeling of being an embodied agentive subject are fundamentally shaped by embodied interactions with other people in early infancy and beyond. Progressively these embodied interactions allow the developing organism to mentalize its homeostasis and hence they constitute the core of our objective subjectivity.

Sensory Systems are Developing in Utero

How might these systems be linked in infancy and what are the implications? First, our sensory systems are developing in utero so that sensory input is being processed even before the infant is born.

 The development of the tactile system

The tactile system is the first system to develop in utero and is the most mature system at birth. By the fifth gestational week, the embryo is able to sense pressure in the lips as well as the nose. By nine weeks gestation pressure is also sensed in the fetal arms, chin, and eyelids, and by 10 weeks the fetus is experiencing sense pressure in the legs. By 14 weeks, a healthy fetus can sense pressure in most of the body. In the fetus’ third trimester the touch sensors in the fetal skin are becoming wired into the insular cortex of the brain where the fetus can respond to the contextual features of touch (Weinstein, 2016, p. 128). Tactile awareness in the back and top of the head does not develop until the infant is born and this may enable the infant to weather the experience of labor and birth (Weinstein, 2016, p. 128). Touch is a primary sense for attachment formation.

The development of sight

The optic primordium cells that are necessary for the development of vision begin to form at about 28 days of gestation and, at approximately two months’ gestation, there are axon connections that form as the eyes grow and move from behind the cranium to their front positions. Between 14 and 28 weeks gestation there are about 100 million neurons that have formed but are not yet connected. The infant can see light through the mother’s belly and amniotic fluid by the last trimester (Weinstein, 2016, p.127).

The development of taste

By eight weeks gestation there are taste buds on the tongue. These buds are further formed around the mouth at 13 weeks. The fetus is able to taste amniotic fluid by four months gestation (Weinstein, 2016, p. 127).

The development of smell

By eight weeks gestation the fetal olfactory sense is near full maturation and by the end of the first trimester the main olfactory subsystem is a functioning sensory system. Smell receptors are functioning by 10 weeks gestation. Thus, the fetal olfactory system is working before the child is born. The smell of amniotic fluid, which is similar to the scent of breastmilk is already beginning to become familiar to the fetus.

Auditory system

Three-and-a-half weeks after fertilization the ears are beginning to differentiate (Weinstein, 2016, p. 126). The fetus is able to hear by the end of the middle of the second trimester (Weinstein, 2016, p. 126). Auditory information can be carried from the ear to the brain by four to five months gestation when the eighth cranial nerve is developed.  Weinstein (2016) notes that the most consistent sounds and rhythms that the fetus is hearing are the mother’s heartbeat as well as her voice. She also adds that the fetus (prenate) can respond to sound as well as indicate sound preferences by 23 weeks gestation and three weeks later is learning intonation, rhythm and other maternal speech patterns. By 34 weeks the fetal auditory threshold levels are comparable to adult preferences (Weinstein, 2016, p. 127).

The development of the proprioceptive and vestibular systems

Beyond the more well-known five senses, the proprioceptive and vestibular systems — ; sixth and seventh respectively — also play important roles in an infant and young child’s development The proprioceptive system functions and enables the infant to feel a sense of location as well as the position of different parts of the body in space and in relation to other animate and inanimate objects. It also enables the infant to have an inner awareness of body posture (Williamson & Anzalone, 2001). Williamson & Anzalone (2001) state that proprioception gives us information about the body’s orientation in space as well as the relation of other body parts to each other, the rate and timing of our movements as we move, the force that our muscles exert, how fast and much our muscles are lengthened or shortened when we engage in activities, and the angles at which each of our joints change as we move. Because the fetus moves in utero, the proprioceptive receptors enable the fetus to practice movements even before the infant is born. (Weinstein, 2016, p. 129). Our proprioceptive sense enables us to develop a schema of our body, i.e., a physical sense of self, an inner awareness of our body parts and how they relate to our larger body systems, and how these parts move through space (Williamson & Anzalone, 2001, p. 9-10).

The vestibular system that is in the bony labyrinth of the skull is also attached to our hearing mechanism. This system is comprised of three structures in our inner ears: the semicircular canals, the saccule, and the utricle. The semicircular canals enable us to register the speed, force, and direction as we turn our heads when we look around or when we swing. The functions of the vestibular system include the regulation of our muscle tone and coordination, our balance and equilibrium, the control of our eye movements so that we can maintain a stable visual field when we move, our maintaining and transitioning of our states of arousal, and our levels of attention (Williamson & Anzalone, 2001, p.8). Vestibular functioning that helps the body’s response to head movement and gravity is functioning early in gestation (Weinstein, 2016, p. 12-129).

What goes on even before an infant is born can impact the architecture and development of the fetus, programming the fetus to the kind of stimulation that will be experienced after birth.

Thus, a calm fetal environment prepares the fetus to engage with a calm postnatal environment. A stressful prenatal environment prepares the fetus to deal with similar stimulation after birth. If the external environment that is experienced after birth is different from the environment that the fetus has experienced in utero, the infant will not be prepared for that environment and this has important consequences for the infant’s interoceptive development and adaptation.

When the baby is born, he or she is placed on the mother’s abdomen and both partners experience body-to-body contact. The mother’s interoceptive system is fully functioning and the experience of the baby’s body on her resonates throughout her system. The experience is on a positive-negative continuum as well as on a high-low arousal intensity. The baby is experiencing visceral stimulation of warmth or coolness, softness or rigidity of the mother’s body, the sounds, intensity of light of the neonatal context. Over time the infant begins to form the seeds of his or her internal working model of the world. These experiences energize the interoceptive systems of both partners and are the earliest components in the development of attachment. When things go right for both the mother and the baby, the roots of a secure attachment begin to be experienced. However, when things do not go well, the stress system for both partners becomes activated. Such experiences may form the earliest foundation and predisposition of mood disturbances. This is an area for further study.

When the Hypothalamic-Pituitary-Adrenal (HPA) system is activated there is an increase of cortisol and the amount of blood that is pumped by the heart increases and the release of epinephrine cause the contractions of the heart muscles to increase. This is an interoceptive signal. When the HPA system in the infant begins to function, the release of these chemicals affect the developing emotional system of the child and most likely impinge on the development of the attachment and social systems. There is not yet data in infants to map the development of the interoceptive system, but we do have the tools to assess changes in the stress and attachment .

Research into the interoceptive system, stress system, and attachment system is imperative. If an infant or toddler has certain experiences or doesn’t have certain experiences, often the outcomes seem inevitable. More continues to be discovered about neurological and systems plasticity every day. Due to these growing discoveries, infant and early childhood professionals need to be proactive but cautious, and evaluations should be longitudinal rather than static and interdisciplinary and collaborative.

Implications for infant mental health

Infant mental health intervention is dyadic intervention; the port of entry is the infant-parent system. The infant affects the family system as the family system affects the infant. This has major implications for intervention. This fits in with interoceptive difficulties as well. In treating infants, toddlers, and preschoolers it is necessary to work with the parent-child system rather than with the infant, toddler, or preschooler alone.

The development of self-regulation is a primary outcome of interoceptive treatment, and this cannot occur unless the parent and infant, toddler, or preschooler are treated together.

Self-regulation is the foundation of mental health adjustment for all of us. If we are not able to modulate our neurophysiology, modulate our sensory systems, or develop control, self-control, and self-regulation we cannot function efficiently within any environment. Engagement, back-and-forth interactions, contingency, sharing, ideas, and eventually healthy reality sense, reality testing, and reality adaptation are dependent upon self-regulation. It starts from the outside (caregiver) being the external regulator,  while the caregiver’s regulatory techniques scaffold the child’s self-regulation skills.

The caregiver acts as a social biofeedback machine in which the infant learns about their internal signals and emotions through the caregiver’s feedback and response to their expressive cues (Buck, 1989). For example, at birth, initially the sensation of hunger is simply a vague, unpleasant feeling and the infant learns through interactions with the caregiver about the meaning and motivational value of the internal sensation of hunger (Harshaw, 2008). Taken together, the infant-caregiver relationship potentially influences the infant’s ability to:

1. Notice internal body signals: The infant recognizes body signals as important constructs that are validated and tended to consistently by the caregiver
2. Connect the body signals to the emotion: The infant begins to accurately interpret body signals through the feedback provided by the caregiver
3. Regulate by using a feel-good action: The infant learns to self-regulate through the observation of the strategies used by the caregiver to co-regulate

Future Considerations

To date, the interoceptive literature has been primarily anatomical and theoretical. Kelly Mahler is a pioneer in intervention with children. Her model fits exquisitely with the infant mental health model of treatment. Presently, her curriculum is used primarily with three-year-olds  and up, but with modifications it can be used with children as young as two. Working with children involves developing a vocabulary of sensations, and then an emotional vocabulary, before developing action strategies. These vocabularies stretch the range of words for sensations and emotions. The work of Lisa Feldman Barrett has shown that our emotional vocabularies tend to be limited and we do not spend time teaching children to differentiate gradients of sensations and emotions. Thus, by working with the dyad, both parent and child are learning about the different interoceptive experiences as well as the gradient of intensities that contribute to our individual differences.

By developing tools and techniques to help infants and toddlers to become maximally aware of their bodies and their interoceptive signals, there is more opportunity for doing preventive interventions. This will broaden the field of infant mental health intervention services. As more research is done on the development of interoception from infancy onward, the melding of interoception with infant mental health will be a powerful combination for treatment. This series of articles provides a beginning for researchers and practitioners to include the literature on interoception as a central foundation concept in infant mental health training programs.

Buck R. Emotional communication in personal relationships: A developmental-interactionist view. In: Hendrick C, editor. Close relationships. Newbury Park, CA: Sage; 1989. pp. 144–163.

Bruch H. Hunger and Instinct. Journal of Nervous and Mental Disease. 1969;149:91–114.

Harshaw, C. (2008). Alimentary epigenetics: A developmental psychobiological systems view of the perception of hunger, thirst and satiety. Developmental Review, 28(4), 541-569.

Oldroyd, K., Pasupathi, M., & Wainryb, C. (2019). Social Antecedents to the Development of Interoception: Attachment Related Processes Are Associated With Interoception. Frontiers in psychology, 10.